The mission will help scientists investigate how planets formed and how life began, as well as improve our understanding of asteroids that could impact Earth, Nasa said in a statement on Wednesday.
The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft will travel to the near-Earth asteroid Bennu and bring a sample back to Earth for intensive study.
"The launch of OSIRIS-REx is the beginning a seven-year journey to return pristine samples from asteroid Bennu," said OSIRIS-REx Principal Investigator Dante Lauretta of the University of Arizona, Tucson.
"The team has built an amazing spacecraft, and we are well-equipped to investigate Bennu and return with our scientific treasure," Lauretta said.
The 2,110-kg fully-fuelled spacecraft will launch aboard an Atlas V 411 rocket during a 34-day launch period that begins on September 8, and reach its asteroid target in 2018.
After a careful survey of Bennu to characterise the asteroid and locate the most promising sample sites, OSIRIS-REx will collect between 60 to 2,000 grams of surface material with its robotic arm and return the sample to Earth via a detachable capsule in 2023, the US space agency said.